A Comprehensive Guide on What causes Arc Flash?

Introduction:

Imagine standing near the sun's surface, around 35,000 F, almost 4 times hotter than the sun. This is the temperature of an arc flash, an electrical explosion that vaporizes metal and causes severe burns, blindness and even fatal injuries. In addition to burns, arc flashes can cause fatal injuries, including severe skin damage and shockwave trauma. An arc flash occurs when a fault in the electrical system suddenly releases huge amounts of energy. In the US, every day, around 5 to 10 arc flash incidents occur daily, causing around 7000 burn injuries and 400 deaths each year. Unlike electrical shock, where current flows through the body, an arc flash releases an intense burst of heat, light, and pressure into the surrounding air. Workplace handling electrical equipment should implement detailed safety protocols to prevent arc flash incidents. In this blog, we will explore the causes of arc flash, its contributing factors and prevention strategies.

Understanding Arc Flash: What It Is and Why It's Dangerous

A low-impedance fault allows electrical current to travel through the air between the conductors or to the ground, resulting in an arc flash. An arc flash produces intense heat and a bright flash, making it a major safety risk.

Key Characteristics of an Arc Flash

The following are the major characteristics of an arc flash:

1. Temperature: Arc flash temperatures range from 5000 to 35000 F (2,800 to 19,400°C), which is almost 4 times hotter than the sun's surface.
2. Explosive Expansion: The enormous amount of energy released during an arc flash swiftly vaporizes metal conductors, causing a rapid & violent expansion. When vaporized, copper expands to 67,000 times its original volume, creating an explosive force.
3. Energy Release: An electrical arc releases an uncontrolled amount of energy which manifests as extreme heat, a pressure wave and blinding light.
4. Arc Flash vs Arc Blast: Arc flash refers to the intense heat and light generated during an electrical arc, whereas arc blast is a supersonic shock wave produced when the arc vaporizes the metal conductors. While both stem from the same arc fault, arc flash and arc blast are two different phenomena. However, the term 'arc flash' is often used to refer to both.

Primary Causes of Arc Flash Incidents

Arc flash incidents occur due to a combination of factors. Understanding these contributing factors helps in effectively implementing the prevention strategies for such incidents.

Equipment Failure and Insulation Breakdown:

Equipment deteriorates with time, weakening the insulation and increasing the risk of arc flash.

• Arcing and overheating occur due to lose or degraded connections, potentially causing an arc to flash. Aging electrical systems lack modern protective features making them more vulnerable to failure as their ability to handle electrical loads diminishes with time.
• Poor quality replacements and DIY fixes of equipment and machinery introduce hidden risks and increase the likelihood of arc flash incidents.
• Poor equipment maintenance can lead to corrosion, expose conductive surfaces, and increase heat and resistance, which are the key causes of arc flash events.

Human Errors:

• Negligence: Workers bypass safety procedures and work in hazardous conditions due to fatigue, distraction, workplace pressure and overconfidence. Human errors and negligence account for 2 out of 3 arc flash incidents.
• Failure to Verify De-energized Equipment: Sometimes, workers neglect lockout/tagout (LOTO) procedure, as they assume that the equipment is safe without verifying its de-energized state.
• Lack of Situational Awareness: Panic or distraction can lead workers to make unsafe decisions, such as accidentally touching live components or bypassing safety controls.
• Ignoring Warning: Failure to wear the required PPE and ignoring the warning labels increase exposure to arc flash hazards, endangering the lives of workers.
• Using Damaged or Non-Insulated Tools: Improper or non-insulated tools increase the risk of arc flash explosions.
• Untrained Workers: Lack of knowledge and training regarding arc flash prevention increases the likelihood of human errors.

Overcharging Circuits and Short Circuits:

• Unintended Arc Faults: Discharge of electricity between the conductors causes dangerous can trigger dangerous arc flash incidents. An unintended contact between an energized conductor and another conductor or grounded surface can also cause an arc flash.
• Voltage Transients (Spikes): Sudden voltage surges caused by reactive load switching or lightning strikes can also trigger arc flashes.

Environmental Factors:

• Dust: Dust accumulation on electrical equipment creates a conductive path that causes arc flashes and short circuits. It also traps heat, increasing the risk of overheating and equipment failure.
• Corrosion: Corrosion degrades electrical components, erodes the insulation, and increases the risk of electrical faults, notably in environments with elevated humidity or corrosive substances.
• Condensation: In poorly ventilated or fluctuating temperature environments, moisture buildup between the conductors can create unintended electrical paths, thereby increasing the risk of arc flash.

Arc Flash Hazards and Consequences:

1. Arc flashes generate extreme heat, causing third-degree burns and potentially fatal injuries.
2. Arc flash causes explosions which hurl molten metals and other debris at lightning speeds, leading to lacerations, eye injuries and puncture wounds.
3. Vaporized metals and insulated materials release toxic fumes that lead to respiratory issues, chronic lung damage and chemical burns.
4. Direct exposure to electric current can result in severe electrocution, ultimately leading to cardiac arrest.
5. The explosive force of arc flash can destroy electrical panels, damage surrounding structures, and result in costly downtime and repairs.

Standard Practices for Preventing the Arc Flash Hazards

Arc flash incidents can be prevented through a combination of proactive measures, thorough maintenance and strict adherence to safety protocols.

Regular Inspections & Maintenance:

• Check electrical equipment regularly for deterioration.
• Detect overheating components with the help of infrared cameras.
• Perform partial discharge testing to detect insulation breakdowns and prevent arcing. Maintain record of all maintenance activities for future reference and compliance.

Engineering Controls Implementation:

• Invest in Arc-Resistant equipment such as switchgear that helps to contain the arc energy.
• Ensure Proper grounding of all the systems to reduce electrical faults to zero.
• Use current limiting devices to reduce the magnitude and duration of the electrical fault.
• Ensure your workplace has marked arc flash boundaries and PPE available for the workers. Workers must wear arc-rated clothing that is ATPV rating appropriate for the hazard levels, face shields with arc-rated balaclavas, insulated gloves, and dielectric boots while working near energized equipment.

Electrical Safety Training for Workers

• Train workers to properly Lockout/Tagout the equipment and de-energize the equipment before maintenance.
• Train your employees to respond to arc flash incidents and use the first-aid kit. The arc-flash first-aid kit should include burn dressings (for example, water-based gel dressings), silver sulfadiazine cream for treating burns, sterile saline for eye irrigation and non-adherent dressing for burn skin coverage.
• In addition, the workers should be educated on how to respond immediately to arc flash incidents by removing burned clothing safely, responding to the signs of electric shocks and using sterile water to cool down the affected areas. To facilitate the workers and employers, we have developed the Arc Flash Safety Training (NFPA 70E), aligning with OSHA general industry standards and the NFPA 70E guidelines. Check out our course, register today and get certified.
• Routinely conduct arc flash risk assessment at your workplace. Using the incident energy calculations, pick out high-risk arc flash areas requiring additional precautions. Mark the arc flash boundaries by defining the safe zones around the equipment. Based on the risk assessment and findings, modify the PPE and work protocols to tackle arc flash hazards accordingly.

For more details on how to avoid common electrical hazards at the workplace, read our blog.

By sticking to these best practices, organizations can reduce arc flash hazards and ensure workers' safety.

The Bottom Line:

Arc flash incidents can occur in an instant, posing a severe threat to life and safety However by implementing the correct SOPs and precautions, you can reduce the risk of such incidents The arc flash-rated PPE, such as insulated gloves, arc-rated coveralls, and face Shields, is a true lifesaver against this hazard. A tiny tear in the arc-flash gear can lead to life-threatening injury in case of an exposure to an arc flash. Train your team to act swiftly in case of an incident and use the first aid kit effectively. Along with PPE, routine risk assessment and checks also play a crucial role. Refurbish the arc flash labels, catch the hidden dangers by running the infrared scans and apply stringent lockout/tagout (LOTO) procedures. Remember, no task is worth an arc flash injury and an incident in the long run.

References:

Fluke, Arc flash vs arc blast, https://www.fluke.com/en/learn/blog/safety/arc-flash-vs-arc-blast

Falcon Power Consultants, Top 10 Arc Flash Statistics Every Employer Should Know, https://falconpowerconsultants.com/top-10-arc-flash-statistics-every-employer-should-know/

G&W electric, What is Arc Flash: Causes, Risks, and Prevention, https://www.gwelectric.com/blog/2024/08/20/what-is-arc-flash-causes-risks-and-prevention/